(a) Field of the Invention
The present invention relates to a liquid crystal display. More particularly, the present invention relates to a liquid crystal display of a vertical alignment (VA) mode type in which the liquid crystal molecules are aligned vertically with respect to upper and lower panels.
(b) Description of the Related Art
Liquid crystal displays have been widely used as flat display devices. Liquid crystal displays typically include two display panels respectively provided with pixel electrodes and a common electrode, and a liquid crystal layer interposed between the two display panels. In the liquid crystal displays, an electric field is generated in the liquid crystal layer by applying a voltage to the pixel electrode and the common electrodes so as to control an alignment of liquid crystal molecules in the liquid crystal layer. Images are displayed by the liquid crystal displays by controlling polarization of incident light using the alignment of the liquid crystal molecules.
Among liquid crystal displays, a vertical alignment mode liquid crystal display (LCD) uses a vertical aligning agent and the liquid crystal molecules are aligned vertically with the upper and lower panels. The vertical alignment mode LCD may obtain a wide viewing angle and a fast response speed compared with a TN (twisted nematic) mode LCD.
In the vertical alignment (VA) mode LCD, as means for achieving a wide viewing angle, cutouts are formed in the field generating electrodes, and protrusions are formed on the field generating electrodes.
In the case of a patterned vertically aligned (PVA) mode LCD having cutouts, the pixels are divided into a plurality of domains by the cutouts of the field generating electrodes, and the liquid crystal molecules have different alignment directions in each domain. That is to say, the cutouts of the lower panel are disposed between the cutouts of the upper panel such that the electric field has a vertical component with the respect to the upper and lower cutouts, and domains having electric fields of different directions are respectively disposed on the upper portion and the lower portion in one pixel. The tilt directions of liquid crystal molecules are formed in four directions such that a reference viewing angle of the liquid crystal display is increased.
In the configuration of cutouts above, the intensity of the electric field is poor in a portion in which the cutouts of the field generating electrode are disposed, compared with the other portions. Accordingly, the liquid crystal molecules disposed in the portions corresponding to the cutouts are rearranged with a slower speed compared with the other liquid crystal molecules inside the domains such that image sticking may be instantly generated.
More particularly, singular points where the direction of the liquid crystal molecule are gathered into one position are not fixed inside the cutouts, and their positions continuously change while driving the liquid crystals, or the generation positions of the singular points are changed for every frame in which the signals of the pixels are changed such that the image sticking may be instantly generated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.